Some Properties of Astronium graveolens Wood Along the Stem

ABSTRACT We investigated the axial variation of specific gravity, shear parallel to the grain and anatomical features of Astronium graveolens wood and related these properties to the anatomy along the stem. We felled five 20-year-old trees and cut discs from four different stem heights, including stem base, 1 meter, 2 meters and 3 meters, for a total of 20 discs, and studied wood samples near the bark and at the base of trunk. Axial variations found appear to provide a balance between mechanical strength of the wood at stem base by the higher density and higher shear by the increase in ray frequency that contributes to locking the vertical cells and growth rings, thus preventing the stem from easily breaking when bent. For hydraulic conductivity, vessels with smaller diameter and frequency at the stem base help prevent the occurrence of embolisms that would reduce water flow along the main stem.

摘要：本研究针对阔变豆木（Astronium graveolens）木材的比重（specific gravity）、顺纹剪切强度（shear parallel to the grain）及解剖特征（anatomical features）的轴向变异（axial variation）展开探究，并将上述特性与树干轴向的解剖结构建立关联。我们采伐5株20年生林木，从树干基部、1米、2米及3米四个不同高度截取圆盘试样，总计20个，并分别对近树皮处与树干基部的木材试样开展分析。

研究发现，观测到的轴向变异呈现出性能平衡机制：树干基部更高的木材密度可提升力学强度，而木射线频率的增加则强化了顺纹剪切性能，该变化有助于固定纵向细胞与生长轮，进而避免树干受弯时轻易发生断裂。

就导水率（hydraulic conductivity）而言，树干基部直径与频率均更小的导管能够有效防止空穴栓塞（embolisms）的发生，此类栓塞会降低主茎的水分传输效率。